Design of an infrared monochromatic system with an AOTF as the dispersion element

In this paper, a method on how to design an infrared monochromatic system based on an acousto-optic tunable filter (AOTF) is introduced. Some key problems about optical system (including collimation of incident light beam and working distance - the shortest distance to separate the zero order light and the diffracted light) are re-searched and solved. The driving circuit for an AOTF based on direct digital synthesis and a digital signal processor is also introduced. The experimental results show a direct proportional relationship between the wave number of diffracted light and the driving frequency. The monochromatic system has a wave number range of 2000-4000 cm^-1a nd the spectral half-width is 20 cm-1